Electronic dilatometer



March 27, 1951 R. l. swANsoN ErAL 2,546,796

ELECTRONIC DI LATOMETER Filed May l5, 1947 3 Sheets-Sheet l ThemGttox'neg March 27, 1951 R. swANsoN ETAL ELECTRONIC DILATOMETER 3Sheets-Sheet 2 Filed May l5 1947 Gttorneg March 27, 1951 R. l. swANsoNET Al.

ELECTRONIC DILATOMETER Filed Mayl, 1947 Iig. 5.

3 sheets-sheet s V/IRMBLE FREQUENCY Osc/mm? FREQUENCY NE TER RECORD/N6PorE/v non@ g FUE!) FREQUENCY Osc/mm? REcoRD//ve PYROMErE/e pay @MEM

Theil Gttorueg amavge ceiving the upper end of the tube and a coaxialupper end I) in the form of a portion of a sphere. End 50 is receivedwith a correspondinglyshaped depression in the bearing block 52, whichis pref-` erably made of dielectric material. It willbe seen, therefore,that changes .in lengtheof the specimen in that portion thereof'betweenthe ends of the tubes 36 and 46 are' accurately transmitted as verticalmotions imparted to bearing block 52. Actuation of-bearing block 52 asde-v scribed operates to change the capacity of the varialcplevcondenser* 55 shown mounted on thetop plate 6 of the frame/ Thestructure of such con`' denser andthemeans whereby it is mounted andactuated will bejclearffrom theexamination of Mounted on the. lowersurface of plate 6 'in a" position coaxial vwith* the specimenis anannular spacerv member 58 made vof vinsulating dielectric material. Suchspacer is retained on the plate by spaced bolts 60, which also retainthe thin diaphragm 56 made of electrically insulating dielectricmaterial such as phenolic resin. Mounted centrally on the diaphragm isVthe lower plate 54 of the. Variable condenser. Such plate, may ifdesired, be VVmade integral with the bearing block 52. .DiaphragmrE ismade of such thine ness and its lateral dimension is such that itexesfreely in a vertical direction within the limits of motion requiredby vexpansion of the specimen. y

.The lupper plate 62 of the variable condenser is adjustably mountedupon plate 6 so that the initialcapacity of the condenser may be changedasdesir'ed. Plate 62 is mounted uponthe lower endof the spindle .64.The.upper end of spindle |54 is'threaded and the lower end thereof iscylindrcal fitting very accurately in the opening- 68 through plate AIi,which functions as a guide. Spindle 64-is keyed to plate' by key .'IIIwhich fits into la". longitudinal keyway'in the'lQWer vun-i threaded endof thespindle.` .l Vertical" adjustment-ofthe spindle 64 is ef fect'edby means of 'thenut 12 which has a flangedlower end 14 fitting withinthe central recess in thaupstanding cupped member 65, securedto the?upper surface of plate'as by being welded thereto. Nut 'I2 'is retainedin member 66 byl means of the washer like retaining'member 'I6interfitting with the flange 'I4 on the nut and with .the verticalcylindrical surface of the nut.v

The nut '|2' is provided with a handwheel 'I8 sfecured to the upper'endthereof by key 88, so that turning of the wheel and the nut raises thespindle and thus plate 62 without ,rotation thereof. The 'spindle may belocated in the desired adjusted position by means of the' locknut 82coacting with the upper end .of nut 12. lIn order ,to minimize'errors'which might be introduced into the system by lateral movement ofcondenser plates'54 and 62 relative to each other, the upper plate. B2is made of smaller diameter than the lower plate 5.4 as shown.Vv

[Electrical connection of the top and bottom plates of thecondenser tothe other elements of the electrical system is effected by a coaxialcable generally designated 84 .which is connected to the condenserplates in the specimen holding-and heating unit by the connectorgenerally Vdesi'ge nated 86. The`parti`cular`connectr shown is one whichis commercially sold under the tradename Amphenol Microphone Connector,which connects the upper plate 6 2 to the outer tube I|8 of the coaxialcable and fthe lowerplate: to the inner conductor |2. The coaxial"cable, which is used to eliminate the introduction of errors 'whichwould occur due to changes in capacity,

if. ordinary lead wires were used, is provided with insulating -beads|22 within the tubular casing I |3which holds the inner conductor |20 ina position coaxial of the casing. The cable is pro vided with an 'outerinsulating layer |24, such layer being 'removed in the Vicinity of theconnector so that tubular casing H8 makes contact with the 'outer body|26 .,of the connector. A coil spring |38 is provided 'adjacent theconnector body iI 2S to stiiien the fcable' and A'prevent excesbody |26is made by a layer of solder |28.

, The connector consists of two main parts, the

male portion |84 being screwed into a tapped opening |88 in the-'plateIi' as shown; The female portion |v is provided with a depending flangenut |36 designed to screw on thev top of the male member. Anelectricalconnectionis effected between the upper condenser plate 52 andthe tubu#l lar member H8 ofthe cablethrough 'spindle 64, plate 6,ma'lemember |04, female member |05; and connector body |25, all`of which aremade of metal. The connection betweenthe'lowercon-v denser plate 54 andthe inner conductor |28 is effected by means of a conductor |28 whichruns from the plate 54 to the connecting-stud-'IIS mounted on insulatingplate I I2 in the upper end of the male member |04. An4 insulating tube|2| prevents the wire |28" from contactingany other metal part. The nut|36 on the femalemember carries within it a slidable insulating vdisc|40 which is urged downwardly by the coil spring |38i Disc |48 carriescentrally thereof in a position confronting stud IIB a similar stud |34attached to the lower end of conductor |20. Thus, when nut Itris screwedon to the male memberY |84, a ti ght contact is made and maintainedbetween studs IIB a nd" |34.v In Figure 3V the' above 'describedconnection between the condenser plates' and the.variablefrequencyoscillator 92 is shown diagrammatically, the condenserplate 54 Vbeing shown directly connected to oscillator l92 by cbn ductor|28, and the plate 62 being shown conf nected thereto by the connection|42 (which consists of the outer shell of the microphone shellconnector), tubular casing I8 and conductor |44. vConnection of thecoaxial cable to the oscillator is effected by a similar microphoneconnector, not shown, and thus connection |44 represents'the outercasing of such second micro'-v phone connector. l

The temperature ofthe vspecimen may readily be observed by the provisionof'a thermocouple 88 positioned in a suitable recess therein, suchthermocouplebeing provided with leads 90 which are conveniently ledltherefrom through opposite openingsin the .upper end ofthe feeler tube46.

The condenser 55 is one element of the cire cuit of variablefrequencyoscillator92, indicated generally'inFigure'S. A s the capacityvof the condenser 55 changes due to contraction or elongation of specimen34 and consequently motion sive 'strain and bending at'this point; Theaxial; connection between casing I i8" andithe connector' 5* mension-oithe specimen such change or sluit in frequency ci oscillation must bemeasured, is accomplished by Velectrically 'coupling the variableoscillator 92 with a vconstant 'frequency oscilla'tor 94. The resultingbeat frequency is ed to frequency meter 96 which is so constructed as tobe sensitive to the subtractive beat frequencies and not 'the additivebea-t frequencies. Fre ouency meter "et develops a voltage which isprop'ortional to the subtraotive beat frequency. *The output lvoltagefrom the frequency lmeter is fed to 'potentiometer -9'8 which 'plots -agraph of lsuch output 'voltage against time. The instrument is 1rFurtherconveniently provided 'with fa recording pyrometer 'ion connected totnermocouple E'8e through 'the leads tu, vsuch "recording pyrometeraiiording a plot of the temperature of the 'specimen vagainst time.

"Various 'commercially available units may be 'employed as the variable'and fixed frequency yos- `eiilato'rs B2 and "et, respectively, thefrequency meter e6, and the recording Apotentiometer anu pyrometer 98and "fou, respectively. In one ernlcodiment of the apparatus the fused'frequency oscillator employed in one 'manufactured by the General RadioCompany and designated Frequency `Monitor "Type '6W5-P, Adescribed andillustrated on pages *132 and T33 of JGeneral Radio 'Company Acatalog K,third edition, T944.

' "In a commercial :installation the variable fre uuency oscillator 9'2and the A'frequency meter "913 are conyeniently combined in one unit, asindicated in'ig'u're '4. In the embodiment described :such combined unitYmay conveniently b'e onelike "wise manufactured by the General RadioCom- 4 plates'a and B12, in the smal-1.portion oi such .-,f

'mvemnt employed during the testing Aof :any one .specimen such vfrequency varies with the -hange df the spacing between .plates fin an`almost `exact straight line relationship, particularly with the `choiceof proper circuitparameters i Thus under the conditions of .use-of-thedilatom- -elter lthe output voltage of the frequency Vmeter variesdirectly, rfor all intents and purposes, as ra straight .line functionof the 'change 'in vertical dimension "of the specimen, and the chartproduced -by recording Apotentiometer 98 may be made to give, uponcalibration of the device and the attendant "circuits, 'direct 'readingsof the dimension changes in whatever units desir-ed. "Calibration of theinstrument will be described below in connection with its operation.

In preparing a test, furnace I4 'is dismantled andfsetaside and nut bis:backed down to 'proyid'e the #necessary clearance for inserting theitest assembly. Thereupon washer 42, pedestal vtube 36, :and specimen 34`are positioned on the 4pl-rc'lestel and nut iil@ is fadvanced to raisethe 'test assembly, upon which ifeele'r tube #'45 aand cap 48 have beenplaced, so that point 5e of the .cap seats within the recess in bearingblock 52. Gi.

Theyert-ical advance Aof nut il) is continued initii-y bearing block 52is displaced Yver-ticaliy to a slight extent, to insure accurate bearingof pointlS of the cap in the recess thereof, but not sufficiently to putany material stress inthe dia-v phragm 56. When such adjustment iscompleted, locknut 44 is Aset up against nut :de to lock 'the pedestalin place.

'The foregoing adjustment establishes thestart'- ing position of lowercondenser plate A54. next step is to 4'adjust the gap between plates 54and v62 `of the condenser 55. rlhis is accomlish'ed by adjusting the gapbetween the plates by 'means of nut 12 until the .frequency of thevariable frequency oscillator 32, previously a-d. justed to anexperimentally predetermined irequency With the microphone 'connector 85disconnected, equals the ire'quency of 'the fixed-irequency oscillator94, at which point the frequency. meter register Thereupon locknut 82isset up againstv nut :12' "to lock plate E2 in position` With the 'testassembly thus .set up andthe zero position of .the vfrequency meterestablished, .iurnace I4 can be positioned around the assembly, thethermocouple 3B connected up, and :initial or cold readings taken.' Theyfurnace may then be operated to heat the vspecimen at :a `.predeter--mined rate, the recording potentiometer and recording pyrometer giving arecord of the .eXp'ansion :of 'the specimen and .its temperature, re-

spectively, `both plotted against `time. 'The times as recorded byinstruments L98 and 1M may. :be coordinated Aas .by :of simultaneousspank discharges through Iportions fof the vcharts 1in the twoinstruments.

`Because :of the almost perfectistraight lime relationship betweenchanges .in :length of the specimens `and the voltage .generated 'bylthe ,frequency meter within the :limits .of use 'of the ydevice, thedilatometer lof the present .invention quite simply calibrated. lIt `isnecessary vonly to determine two points, preferably Well spaced, on thestraight line oi the plot of voltage :generated by the frequency meteragainst change in lmgth of the specimen. Such two points obviously ilocate .the :line and all points intermediate there between as wellasthose a lsubstantial distance ybeyond them in either direction..suitably one such point may be the zero reading Arat atmos .pherictemperature, previously described, yand the :other `a point obtained :bydisplacing upper plate 62 :of the condenser .55 ian additional knowndistance very Iaccurately determined through ithe use of handwheel 'i8andthe .fine screw vthread :of spindle 64, the voltage developed by thexfrequency meter lthereupon being noted.

The scale on which the .cha-rt -produced :by the recording potentiometerle may Abe vchanged as desired. The scale of the ,time-.coordinate'is ofcourse, changed merely by altering the speed at which the chart passesthe recording-pen. scale `of the voltage coordinate is ldetermined bythe .magnitude of the Voltage/output of '.therequency meter. =-Suchmagnitude, which :may be varied within wide limits, maybe set veryfaccurately and .remains constant when so set, `so :that substantially`no additional .error vis introduced into the reading. Thus thedilatometer of to `be understood that the invention is capable ofconsiderable variation as to details. WhatV we claim as new, therefore,is comprehended withinthe scope of the following claims.

,'We claim: v

12. In an electronic dilatometer a specimenq holding and heating unitwhich comprises a frame having a horizontal base plate, a plurality ofvertical standards connected thereto, a spaced horizontal upperplatesupported thereby, anadjustable pedestal supported on 'the base plate,means on such pedestal to support a specimen to be tested, a condensermounted on the upper plate in line with the pedestal and specimen, thecondenser having an upper` horizontal plateY adjustably. mounted on theupper plate of the frame and a lower horizontal plate confrontingv theupper plate and guided for motion toward' and from the upper p late, themeans for guiding and positioning said lower condenser plate comprisinga dielectric diaphragm of which the' plate is mounted, a ieeler memberbetween the upper end of the specimen and the lower condenser platewhereby changes in length of the specimen effect changes .in thevertical position of such lower plate, and a furnace having a verticalopening therethrough adapted to iit about the specimen and to nt closelythe specimen supporting means on the pedestal and the eeler member.

v2. In an electronic dilatometer a specimen holding and heating' unitwhich comprises a frame having a horizontal base plate, a plurality ofvertical standards connected thereto, a spaced horizontal upper platesupported thereby, an adjustable pedestal supported on the base plate, avertical quartz member on such pedestal to support a specimen to betested, a condenser mounted on the upper plate in line with the pedestaland specimen, the condenser having an upper horizontal plate adjustablyymounted on the upper plate of the frame and a lower horizontal plateconfronting the upper plate and guided for motion toward and from theupper plate, the

means for guiding and positioning said lower` condenser plate comprisingan annular spacing member surrounding the condenser plates and securedto the upper plate oi the frame, a dielectric diaphragm secured acrossthe lower edge of the spacingV member, the lower condenser plate beingsecured to the diaphragm centrally thereof, a quartz feeler memberbetween the upper end of the specimen and the lower condenser platewhereby changes in length of the specimen eect changes in the verticalposition of such lower plate, and a furnace having a vertical openingtherethrough adapted to t about the specimen and to t closely thespecimen supporting means on the pedestal and the feeler member.

3. In an electronic dilatometer a specimen holding and heating unitwhich comprises a frame having a horizontal base plate, a plurality ofYvertical standards connected thereto, a spaced horizontal upper platesupported thereby, an adjustable pedestal supported on the base plate, avertical quartz member on such pedestal to support a specimen to betested, a condenser mounted on the upper plate in line with the pedestaland specimen, the condenser-having an upper horizontal plate adjustablymounted on the upper plate of the frame and lower horizontal plateconfronting the upper plate and guided for motion toward and from theupper plate, the means for guiding and positioning said lower condenserplate comprising an annular spacing member surrounding the condenserplates and secured to the upper plate ofthe frame, a dielectric dia-.v A

phragm secured across the lower edge of the spac-- ing member, the lowercondenser plate being secured to the diaphragm. centrally thereof, aquartz feeler member between the upper end of the specimen Yand thelower condenser plate wherebychanges in length of the specimen effectchanges in the vertical position of such lower plate, and a furnacehaving a vertical opening therethrough adapted to lit about the specimenandto iit closely the specimen supporting means on the pedestal and thefeeler member, the frame being provided vwith frame leveling means, suchmeans comprising at least two spaced leveling screws engaging a basesupport and a plumb bob dependent from an upper portion of the frame.

4. An electronic dilatometer comprising a fur-f nace having an openingthrough a Wall thereof, means to support a specimen'to be tested in thefurnace, a condenser mounted substantially in line with said furnaceopening, the condenser having a relatively xed plate and a relativelymovable plate between the relatively xed plate and the furnace, adielectric diaphragm for supporting said movable plate, means interposedbetween the specimen and the movable condenser plate for moving suchplate in vaccordance with changes in a dimension of the specimen, saidlast named means comprising a member bearing on the end ofsaid specimen,a cap mounted on said member and a ball and socket connection betweensaid cap and said diaphragm, a variable frequency oscillator in theoscillating circuit of which the condenser is connected, and means todetect a change in frequency of the oscillator upon movement of themovable condenser plate relative to the xed condenser plate.

5. An electronic dilatometer comprising'a furnace having an openingthrough the upper wall changes in height of the specimen, a variablefrequency oscillator in the oscillating circuit of which the condenseris connected, meansto detect a change in frequency of the oscillatorupon movement of the lower condenser plate relative to the i-lrstcondenser plate, and means fed by the last named means to give a directreading of the change in height of the specimen.

RALPH I. SWANSON. WARREN K. SMITH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,716,796 Rockwell June ll, 19292,322,681 Zenor June 22, 1943 2,351,572 Kingston June 13, 1944 2,367,866Humphreysl et al. "Jan, 23, 1945 2,409,669 Dietert Oct. 22, 1946

